(CNN) The Citadel, a public military college in South Carolina, says it is investigating photos posted on social media that show cadets wearing pillowcases over their heads — costumes reminiscent of the Ku Klux Klan.

The school will begin suspension proceedings for involved cadets, school President Lt. Gen. John W. Rosa said in a statement.

“These images are not consistent with our core values of honor, duty and respect,” Rosa said, calling the photos “offensive and disturbing.”

The photos show an upper-class student in front of seven cadets, the statement said. The cadets are wearing white pants, white T-shirts and white pillowcases with eye holes while holding pieces of paper in front of their eyes.

Preliminary reports are that the students “were singing Christmas carols as part of a ‘Ghosts of Christmas Past’ skit,” the statement said.

The Citadel, founded in 1842, has about 2,300 undergraduates making up the Corps of Cadets, the school website says.